Unscratchable gold is harder than steel

By combining a gold alloy with boron carbide, an extremely hard ceramic that’s used in bulletproof vests, a Swiss team of EPFL researchers succeeded in making the world’s toughest 18-karat gold (75% gold). With a Vickers hardness number of 1000, it’s harder than most tempered steels (600 Vickers) and thus almost impossible to scratch, except with a diamond. This discovery is the result of a three-year collaboration between the Mechanical Metallurgy Laboratory in EPFL’s Institute of Materials, under the leadership of Professor Andreas Mortensen, and the Swiss watchmaking company Hublot — via redwolf.newsvine.com